Process for dewaxing oil



3 sheets-sheet 1 H. F. FISHER PROCESS FOR DEWAXING OIL Filed Jan. l1, 1937 YNN Nolr. 17, 1942.

INVENTOR. Harman f.' FIS/7er ATTORNEY.

NOV. 17, 1942. H F, FlSHER n PROCESS FOR DEWAXING OIL 3 Sheets-Shee't'R Filed Jan. l1, 1937 INVENTQR. Harmon F Fisher BY W0/ ATTORNEY,

Nov. 17, 1942. H. F. FISHER 2,302,386

PROCESS FOR DEWAXING OIL NVENIOR. Harmon F.' Fisher ATToRNEY.

Patented Nov. 17.', 1942v UNITED STATES PATENT OFFICE rnocnss ron nnwAxiNG on. Harmon F. Fisher, Los Angeles, Calif., assignor t6 Union Oil Company of California, Los Angeles, Calif., a corporation of California Appunti@ January 11, 1937, vseran No. 119,998

(ci. coi-1x4) 4Claims.

This invention relates to the separation of precipitates such as wax, asphalt, resin and like substances from oils, and particularly to the elec'- trical separation of hydrocarbon oils from waxes which they contain to produce relatively oil-free high melting point waxes.

Many oils such as lubricating oil, iuelvoil, motor fuel and other similar oils which were derived from crude oils contain parailinic, waxy, asphaltic and resinous constituents which may appear there by reason of having been present in the crude oil from which they were derived or by reason of their formation in intermediate treating processes, such as distillation or cracking. The wax-like constituents which may thus be present limits the minimum temperature at which these oils can be used by solidifying or congealing at lowl temperatures. The asphaltic and resinous bodies also are objectionable for numerous other reasons well known in the art of lubricating oil and motor fuel refining. Therefore in the refining of such oils, it is commo'n practice to remove a substantial portion of these wm asphaltic and resinous constituents in order to lower the pour points and improve the quality of such oils.

The separation ofthe undesirable parailinic and waxy bodies from oil fractions has been accomplished in the past by several processes, the most common and oldest of which are the cold settling process and the cold pressing process. These processes have been ineilcient, time consuming, mechanically involved and have heretofore produced separated constituents having a high percentage of oil contamination.

' Asphaltic, resinous and tarry constituents and color bodies have been separated by well known processes employing acid, alkali, clay or other chemical treatment and recently by solvents. In the solvent process the oil containing the undesirable constituents such as asphalt, resin, color bodies and the like, is dissolved in a quantity'of a suitable diluent such as liquid propane ori other liquid normally gaseous hydrocarbon which has preferably at normal temperature a low solvent power for these bodies, while at the same time retaining practically complete solvent power for the desirable fractions of the oil. Such solvent treatment results in the rejection ofasphaltic bodies from the oil diluent solution in the form of a relatively heavy insoluble precipitatey or as av heavy liquid phase. a substantial portion of which may bel separated from the oil solution by settling in a reasonable length of time. In this solvent process, however, not only a suilicient quantity of the precipitate material often remains 'esses for the separation of wax, paraffin, asphaltic, tarry, resinous and color bodies from oils and to provide an improved process for .the separation of these substances from oil which would be elcient, economical, of high capacity and rapid in action, less costly in time and equipment than processes heretofore employed. The particular object of this invention is to provide -a method whereby the separated constituents, such as wax separated from hydrocarbon oils will be more thoroughly'deoiled and freer from contamination.

.by oily constituents than has heretofore been possible except where special and costly processes have been additionally employed for this purpose. Another object of this invention is to provide a process for separating the wax from waxbearing oil wherein an improved recovery of oil from the wax is accomplished, resulting in a larger unit yield of dewaxed oil.

In general these objects are obtained according to the invention by subjecting the oil .containing the suspended precipitate bodies to the action of an electric field and vigorously washing the electrically separated precipitate bodies lby a relatively large quantityl of recycled wash solvent.

Accordingly the invention resides in an improved process and apparatus for the electrodeposition of the suspended precipitates from oils wherein the oil precipitate mixture is placed in the form of a relatively thin layer upon an inclined moving belt electrode and subjected there to an intense ionizing electric field whereby the .precipitate is deposited and held in a dense layer upon the moving electrode surface, thus effecting the separation of a major portion of the oil from the precipitate and whereby the precipitate layer thus separated from the oil may subsequently 4be thoroughly washed and further electrically treated to remove occluded and adhering oil to pro.-

' duce a relatively oil-free precipitate and a maxipended materials.

This process is particularly adapted and finds one of its major industrial applications to processes for the separation of waxes from oilto produce high pour point oils relatively free from'wax and high melting puin:- wsxes tively free from oil. lt is a particular advantage ci' the process that in contradistinction to processes of settling, centrifuging or filtering, a. careful preparation of the wax precipitate, that is as to crystal structure or plasticity, is unnecessary and avoided. In fact all that is required is to separate the wax as a solid phase by chilling or otherwise precipitating it by reducing the solubility of the wax in the solvent or oil. We have found that the process works particularly well with flash chilled waxes,

vthatis, those waxes formed by such rapid chilling Fig. 3 is a general arrangement of the apparatus;

4-8 in Fig l;

Figs. 5, e, 'z and s illustrate methods er shaping the belt electrode to carry the liquid undergoing treatment and maintaining it in alignment on the drums.

The apparatus is as follows:

. The main elements of the treaters are housed within a vapor-tight shell l provided with a removable end Il, the whole housing being covered by suitable heat insulating material l2. Inside of the container IB an A shaped, movable belt electrode I3 extends between and'around the four rotatable metal drums N to l1 which are in turn rotatably supported upon shafts i8 to 2l extending through the pairs of bearings 22 to 25 respectively. 'Il'ie belt electrode may be constructed of any suitable conducting 'material such as flexible mrtal webbing or fabric suitably impregnated with conductive material such as sprayed or deposited metal or fabric belting covered with a metallic sheeting, but it is preferably constructed of a metallic conducting material having a smooth polished working surface to facilitate the complete removal of deposited material. A belt electrode of this type maybe satisfactorily cone structed of nonLannealed chrome nickel alloy steel sheets, 0.01 inch thick and of any suitable width, with electrically Welded lap joints. A triangular shaped angle iron frame 26 is provided for supporting and maintaining the proper separation and alignment of the said pairs of bearings 22-25. The bearings 2li-2Q are suitably bolted to the corners formed by the intersecting members of the triangular shaped frame 2B while the bearings 25 carrying the shaft 2l are movably supported between the upright angle iron members as shown at 28 and 29 in order to provide vertical movement of the drum i1 suicient to maintain the metal belt I3 in proper tension. The bearings 25 carrying shaft 2l and drum i1 is forced upward against the metal belt I3 by means of coil springs 3G. Tension in these springs is adjustable by means of a bolt 3|.

The tw@ uppermost inclined surfaces 32 and 33 of the metal belt are supported to prevent sag.

ging by means of a plurality of metal rollers 35 which extend across the width of the under sur- Fig. 4 is a partial cross section taken at line electrode.

face of the belt and which in turn are rotatably supported at their ends upon suitable bearings carried by angle irons 3l and 21. 'I'hese angle irons and 31 extend along the edge of the metal belt and are supported in place by means of angle iron clips 3l, 4l, 4I and 42.

Standing at each of the lower four corners of the triangular iron frame 2t substantially directly above each of the lower drum shaft bearings is a high tension insulator as indicated at 4I and 43. From the tops of the four insulators is supported a substantially triangular metallic framework which constitutes the support for the pointed ionizing electrode system. This electrode supporting system comprises angle irons l1 and 68 between which extend a plurality of transverse metal bars forming a gridwo'rk which extends above and substantially parallel with the upper inclined surfaces of the metal belt and also around and below the drum Il as illustrated at 49. From these transverse metal ro'ds forming the gridwork extend the plurality of ionizing electrodes as illustrated at 50. These ionizing electrodes may be constructed of metal wires approximately 6 inches long andi/i6" in diameter, preferably sharply pointed at the unsupported ends which are most adjacent to the metal belt These ionizing electrodes may be spaced approximately at 1 to 2 inch centers.

The electrode system just described is maintained at a high electric potential difference with f respect 'to the adjacent surface of the'belt electrode by means of a suitable high potential gen- `erator 52, which is electrically connected through the high tension lead-in insulator 5I and the ilexible conductor M. The opposite electrical circuit from the high potential generator 52 is completed tothe belt electrode by way of the ground connection 55, through the container I0 and the metallic belt electrode supporting mechanism.

A plurality of nozzles --65 are supported by their connecting pipes from the walls of container i0 and positioned adjacentthe working surface of the metal belt electrode so that liquid supplied thereto can be jetted upon the belt surface through the ionizing electric field at the various points illustrated.

-A scraper 81 bears across the width of the me- 'talllc` belt I3 at a point approximately midway between the supporting drums I4 and I1 and serves to move the deposited material adhering to the active belt surface. A roller 68 extends across the. belt surface at a point opposite the line of contact of the scraper 61 to receive the pressure from the scraper which is applied to the belt surface by means of spring 69. A hopper 10 having a rectangular shaped top opening is provided directly below the scraper 61 to receive deposited material removed from the belt and to guide this material into the screw conveyor 12 by means of which the deposited material is removed from the treater and introduced into the accumulator 15. A heating coil 16 serves to introduce heat into the bottom of the accumulator and an outlet connection 11 carrying valve 1B serves to drain accumulated liquid material. The screw conveyer 12 is permanently supported from the bottom surface of the container l0 by means of suitable supports 13 and is driven by means of pulley 89 whichis connected to shaft 8l which in turn extends into-the accumulator 15 and into the treater through a bearing and stulllng box 82.

The primary framework 2B together with all of the associated mechanical and electrical apvment of the metal belt.

paratus hereinbefore described; which includes the drums |4--I|, the metal belt electrodev I3 andthe ionizing electrode system comprising the electrodes 50 and their supporting gridwork, is movably supported upon four grooved metal wheels 85-88. These grooved metal wheels rest upon two rails 89 and 90 which. extend across the width'of the container I0 so that upon removal of the end Il the whole treater assembly 'can be readily rolled out of the container and repaired or replaced by another similar unit. The container as illustrated at may be sufficiently long to contain a number of these treater units, any one of which may thus ybe readily removed from the container for repairs or replacement with a minimum of lost time.

The belt electrode and the supporting drums are driven by means of pulley 92 which is attached to the end of shafting 93 which passes into the container I0 through the bearing and stuiiing box 94. The Iflexible splined coupling 95 is provided for connecting the shaft 93 to the end of the drum shaft I8.

In the Opposite sides of the container |0 and. directly beneath the lower drums Il and I 6 is provided rectangular reservoirs |00 and IM. formed by means .of the metal partitions |02 and |03 respectively which also constitute the flange portion of the before mentioned rails 09 and 90. These reservoirs are provided for collecting liquids which have been treated on the belt electrode surface and which drain therefrom at these points. Provision is made for withdrawspillage of th oil.

illustrated in Figs. 6-8 is in the resultant raising of the belt edge as shown in such a manner as to conne the applied waxy oil layer to the belt surface. This raising of the belt edges eliminates the necessity for providing special dams bearingl upon the moving belt edge to prevent The invention accordingly also resides in the special roller` means for maintaining stable alignment of the metal belt and for retaining the 'waxy oil mixture upon the belt surface..

The herein described apparatus is adapted to perform the process of electrically separating precipitates and solids from oils in general. It is particularly adapted to separate wax, asphalt and color bodies from lubricating oils, waxy, resinous and colored bodies from gasoline and Diesel fuel oil, asphaltic and carbonaceous substances from residuums and tars from coal tar oils and the like.' It is also adaptable to the separation of high melting point waxes, fats and fatty acids from animal or vegetable oils containing them.

Since the process and operation of the apparatus for the separation of any one of these substances from oil is similar, the following typical operation as applied to electrical Adewaxing of wax-bearing oil is given for example.

The wax precipitate may be formed in the wax-bearing oil preparatory to the electrical deedge portions as illustrated in Fig. 5. As the.

metal belt moves from one side of the pulley to the other one or the other of its edges comes' in contact with the upturned end portions 'of the drum, resulting in increased tension and elongation along that contacted edge. This -elongation has the effect of curving and guiding the belt away from the upturned edge and to the center of the drum surface. The metal belt with this arrangement may thus oscillate slightly yfrom sideto side but remains stable and without departing materially from the desired alignment.

Other means as illustrated in- Figs. 6-8 may be successfully employed for maintaining align-- A number of rollers 35a with upturned or conically shaped ends of increased diameter may be substituted for the rollers 35 shown in Fig. 1, with results similar to that obtained with the before mentioned specially shaped drums.

Another method optional to that illustrated in Figs. 6 and 7 is shown in Fig. 8. Here a single pair or a plurality of pairs of. crowned rollers 35h may be employed to exert the necessary pressure upon the edges of the metal belt to retain its proper alignment. The rollers 35h may be supported at the end shafts |45 upon suitable bearings, variable as to height so as to adjust the desired belt edge pressure.

Another desirable feature of the apparatus as waxing process by any suitable means such as by chilling in the presence of a suitable diluent by indirect heat exchange with a suitable refrigerant, or it may be formed by direct internal refrigeration in the presence of a liquid normally gaseous diluent such as propane. The wax precipitate is preferably formed by the latter self refrigeration method wherein a wax-bearing-oillliquid-propane solution is'continuously flashed into a region of low pressure accompanied by the rapid evaporation of a portion of the. propane and the resulting sudden chilling and precipitation lof the wax in the remaining oil propane solution. Rapid chilling such as this is known as ash chilling" or shock chilling andvappatently results in the formation yof a finer wax precipitate than is formed by slower cooling methods. 'I'he formation of such fine precipitates is advantageous in the electrical dewaxing process. x

In the present process the warm wax-bearing oil feed preferably prediluted with a diluent such as liquid propane in the proportion of 1/2-11/2 tov 1 so as to be suillci'ently fluid to be readily pumped, is supplied through line I|0 and meets y and mixes with the liquid propane diluent from` line III and enters the chiller C through line I|2 where, at a reduced pressure and a resulting evaporation of a portion of the propane the temperature is reduced sufficiently to precipitate wax in the oil propane mixture. Sufficient propane is generally added at this point through line ||I to form a remaining solution having an effective propane oil ratio, after evaporative refrigeration, of from 2 to 6 volumes of propane to one volume of oil. It is preferable to operate with an effective propane oil ratio of approximately 21/2 to 1.

The propane oil mixture .generally at a ratio of approximately 21/2 to 1 and at a temperature of approximately 35 F. containing the precipitated wax, is withdrawn from the bottom of the chiller C through line II3 by means of pump gravity toward the drum I8. The thus applied wax-bearing oil diluent layer containing precipitated wax is subjected to an intense ionizing electric field between the lower points of the adjacent pointed electrodes and the upper belt surface resulting in the electrodeposition of the wax in a dense coating upon the upward moving belt surface. The oil propane mixtu 'e thus relieved of the precipitated wax continues downward under the inuence of gravity over the belt surface and over the deposited wax layer and drops therefrom at the underneath surface of the drum ii into the reservoir IBI and is removed from the electric treater container through pipe |06. 'The thus removed dewaxed oil is forced by pump IIB through the heat interchanger ||1 and through line H8 to a suitable depropanizing still where the propane diluent content of the dewaxed oil is evaporated. The dewaxed oil from which the propane diluent has thus been removed is transported to storage. The evaporated propane diluent is subsequently recovered by compression and condensation and returned to the treating system.

The electrically deposited wax layer travels upon the upward-moving belt towards the drum IS during which travel it is subjected to continued electrical treatment from the ionizing electrodes and to, simultaneous washing by a liquidpropane spray from nozzle 6I. The washed deposited wax layer continues over the drum l and downward toward the drum I4 during which time it may be subjected to vigorous scrubbing by means of additional liquid propane sprays from nozzles 62, B3 and 64 and to simultaneous electric treatment from the adjacent pointed ionizing electrodes. The liquid propane wash containing a small percentage of oil and wax which is 4removed from the thus electrically treated and scrubbed deposited wax layer drops from the belt at the lower side of the drum I6 into the reservoir |03 from which it is wit through pipe |05. The thus withdrawn propane may be recirculated at any desirable rate by means of pump through return line |2| to any of the spray nozzles 6| to 65 in any desirable proportion regulatable by means of valves |22|21. For example the recirculation rate distributed to the wash sprays may be from say l to l0 times the quantity of propane utilized for diluting the waxy oil feed.

Ordinarily in operation the liquid propane supply from the beforementioned propane recovery system is supplied to the treater system through line |30, heat exchanger H1, lines |32 which is the last spray to contact the treated deposited wax prior to its removal from the belt by means, of the scraper 61.. The liquid propane is thus supplied to the system in sufficient quantity to replace that which is continually withdrawn from the propane wash circulating system through lines III to be mixed with the oil feed entering the chiller C through line H2 and to replace that withdrawn from the treater with the treatedwax and oil. The liquid propane thus supplied through line |36 is the approximate quantity Inecessary 'to be added to the oil feed through line\| i i to maintain the desired propane oil ratio in the chiller C. Under these operating conditions, valve E21 is normally closed and valve Under this condition, valve |20 is closed and and |33 and valve |34 to the spray nozzle Sii'` through valve iZS directly to either or both of valve |23 is open.

The dewaxlng operation may be satisfactorily carried on without employing any wash spray from nozzle Il, depending entirely upon the washing effected by sprays n n.

However, it has been found at times desirable to supply fresh liquid propane wash to spray Il to control the propane-oil ratio upon the treating surface or the depositing electrode suriwe- ,and to supply make-up propane to compensate for that lost at this point of treatment by evaporation from the thin film of the waxy mixture running down over the depositing surface.

The wash propane is maintained at a temperature sumclently low to prevent appreciable redissolving of the deposited wax, and the make-up liquid propane supply entering through line III may be adequately precooled by suitable means 'such as heat interchanger |I1 to maintain this temperature-solubility condition. Additional precooling means may be employed if necessary. However, the temperature of the incoming propane may be adjusted to cause partial solution of the depositedwax if desired. The eifect of the propane spray is obviously to thoroughly scrub the deposited wax layer and to remove a substantial portion of the included and adhering oil which has been sweated from the compactly deposited wax layer under the influence of the intense ionized electric field. This scrubbing and washing thus produces a recovered wax which is substantially more oil-free than would be possible by simple electrodeposition alone.

A particular feature of this invention resides in the recirculation by means of pump |20 to the sprays 32--8lof a large volume of wash propane without increasing the over-all propaneoil ratio as would be ordinarily necessary where such recirculation was not employed and where an independent stream of propane from the propane supply system was so employed, all of which was subsequently added to the oil feed. In other words, heretofore in similar processes for electrical dewaxing the quantity of wash propane employed to free the deposited wax from oil has been necessarily limited to that which was required to maintain the proper oil-propane ratio of the feed mixture. Any increase in wash propane heretofore had resulted in an undesirably high propane-oil ratio of the feed mixture.

The recirculation of a relatively large volume of wash propane to the wash sprays also results in producing a recovered wax which is substantially more oil-free than would be possible by washing only with the volume of propane necessary for dilution of the oil feed to the proper propane-oil ratio as has been `the method heretofore.

The deposited washed wax is removed from the belt electrode surface by means of the scraper 61 and is guided by means of funnel 10 into the wax screw 12 by means of which it is withdrawn from the treater and forced into the wax accumulator 15. The wax is melted and freed of propane by means of heat introduced into the accumulator 15 through the coil 1S and the resulting depropanized liquid wax withdrawn to storage through line 11 and valve 18. The wax thus removed from the electric treater constitutes the finished relatively oil-free high melting point wax and may be delivered to storage through suitable means. The propane vapors are exhausted from the wax accumulator 15 to asoasaa apparatus illustratedl is designed to make posthe propane recovery system through pipe |41 and valve |40.

The temperature ofthe contents of chiller C is regulated by varying the pressure therein by means of valve |31 which governs the amount of evaporation ol.' the propane. `The resultingy vapors are withdrawn through line |38 to the before mentioned liquid propane recoveryfsystem.

atmosphere o! propane vapor .confined within the treater shell. When other volatile diluents are employed the atmosphere within the treater shell will consist oi' vapors of such diluents. The

'process is not limited, however. to the use of volatile diluents, certain substantiallylnon-volatile diluents. such as kerosene and gas oil and medium heavy hydrocarbon fractions being frequently employed under some conditions and when these are employed, other suitable means for refrigeration are employed. The character of the gaseous atmosphere maintained within the I notintended to be limiting. The invention intreater shell, although having some bearing thereupon, is not of primary importance insofar as the electrical ionization effects of the electric treating ilelds vare concerned. It is of course y necessary to avoid inflammable gaseous mixtures.

The ionizing electrodes 50 are constructed.

preferably of pointed wires which may be, as stated hereinbefore, 11| to inch lin diameter and from 6 to 12 inches long, and they are supported at their upper ends from the supporting gridwork with `their axes perpendicular to the outer surfaces of the belt electrode. These outer surface of the belt electrode and adjusted at a distance just s'uiilcient to prevent continuous spark-over therebetween at the operating potentials. 'I'he operating potentials which have been found to be effective for eiilcient dewaxing of the oil and eilicient deoiling of the deposited wax, are in the neighborhood of 50,000 to 100,000 voltsl sible the separate collection of wash propane deoiled wax and dewaxed oil. Another advantage of this invention resides` in the unitary structure of the treater and means by which it can be `readily rolled from the container and thus be made completely accessible for repairs or adjustments or for replacement by an entire unit.

Other volatile diluents and wash liquids such vas liquid ethane, butane, naphtha and gasoline may be employed in the hereinbefore described processes. Certain non-volatile diluents such as kerosene, gas oil and even light lubricating oil fractions may be also employed.y When nonvolatile diiuents and wash solvents are employed, the refrigeration steps of the process may be/ accompanied by indirect heat exchange with suitable refrigerants through suitable heat interchangers.

The foregoing is merely illustrative of the apparatus and process of the invention and 'is waxl precipitate from the oi1,'subjecting`the separated wax precipitate to washing with a .wash solventi to remove occluded and adhering oil, removing wash solvent from the separated wax precipitate, and commingling the said removed wash solvent with the said wax-bearing oil mixy ture," subjecting the separated'wax precipitate to a second washing. with wash solvent to vremove additional included oil, separately removing and collecting yfthe wash solvent from the second washing of the separated wax precipitate and recycling said separately collected wash solvent 'to said second washing of separated wax precipitate.v l

2. A'process according to claim 1- in which the recycled second wash solvent is applied to the separated wax at a plurality oi. points.

and under these conditionsof voltage and electrode spacing a silent electric discharge or corona 3. 'A process ,for deoiling wax comprising diluting-the wax-bearing oil with a quantity of solvent, precipitating the wax in the wax-bearing oil solution, subjecting the mixture to -an electric lfield to separate the wax precipitate from the is observed at the ends of the pointedv electrodes extending toward the belt electrodesurface upon which the wax-bearing oil to be treated is iiowed Vrately collected wash. solvent to said second '05 this invention/reside in the separation of`the` washing stage from the treating -stage of the treater whereby the wash propane canbe` sepa- 'rately collected and recirculated to the wash sprays in large quantity without lx1-any way affecting the overall propane-oil ratio.' The oil solution, subjecting the separated wax precipitate to washing with a wash solvent to remove occluded and adhering oil, removing wash solvent from the separated wax precipitate and commingling the said 'removed wash solvent with the said wax-bearing oil mixture, subjecting the separated wax precipitate to a second washing with wash solvent to remove additional occluded oil, separately removing and collecting the wash solvent from the Asecond washing of the separated wax precipitate andrecycling said sepawashingo'f separated walnprecipitate. Y

4. A process according to claim 3 in which the secondwash solvent is recycled to the l.second washing of separated wax precipitate at a rate greater than that at which' diluent is added to the waxy oil feed prior to precipitation or the wax.

\` marron arianna. 

